/*
 * Created at Sep 2, 2011T5:39:27 PM+02.
 *
 * File: ReverseStringRoutine.java
 */
package com.mycompany.silexample;

import java.util.*;

import com.keplerrominfo.common.util.MutableString;
import com.keplerrominfo.sil.lang.*;
import com.keplerrominfo.sil.lang.type.TypeInst;
import com.keplerrominfo.sil.lang.SILValue;
import com.keplerrominfo.sil.lang.SILValueFactory;

/**
 * Reverses a string
 *
 * @author Radu Dumitriu (rdumitriu@gmail.com)
 * @since 1.0
 */
public class ReverseStringRoutine extends AbstractRoutine<MutableString> {
    private static final SILType[][] types = {{ TypeInst.STRING }}; //all possible type combinations are listed here

    public ReverseStringRoutine(String name) {
        super(name, types);
    }

    /**
     * Returns the type of the returned value. For routines that return
     * a value of variable type, this should return null
     *
     * @return the type of the returned value
     */
    @Override
    public SILType<MutableString> getReturnType() {
        return TypeInst.STRING;
    }

    /**
     * The execution of the routine
     * @param silValues the list of values (parameters)
     * @return the SIL value
     */
    @Override
    protected SILValue<MutableString> executeRoutine(SILContext context, List<SILValue<?>> silValues) {

        //AbstractRoutine checks the parameters and their types
        SILValue param = silValues.get(0);

        //We know for sure this is a string
        String val = param.toStringValue();

        //we calculate the reversed value
        String reversedVal = new StringBuilder(val).reverse().toString();

        //We'll prepare the return here
        return SILValueFactory.string(reversedVal);
    }

    /**
     * This returns the description of the parameters
     * @return the part that will be appended to the routine at editing time
     */
    @Override
    public String getParams() {
        return "(str)"; //that's all
    }
}

@Override
public void doAtLaunch() {
    super.doAtLaunch();

    //register the routine
    RoutineRegistry.register(new ReverseStringRoutine("myReverseString"));
}

@Override
public void doAtStop() {
    //first, make sure that super is called, even if will have an exception here
    try {
        //unregister the routine
        RoutineRegistry.unregister("myReverseString");
    } catch(Exception e) {
        LOG.error("Failed to unregister!", e);
    }
    
    super.doAtStop();
}

Don't forget to unit test your code (the above example lacks it, but you should feel obliged to do it).

string myString = myReverseString("KeplercPrime"); //relpeK